Method of Processing a Bituminous Feed By Staged Addition of a Bridging Liquid

ABSTRACT

The present disclosure relates to a method of processing a bituminous feed. The bituminous feed is contacted with an extraction liquor to form a slurry. A bridging liquid is added to the slurry in at least two stages and solids within the slurry are agitated to form an agglomerated slurry comprising agglomerated solids and a low solids bitumen extract. The agglomerates are then separated from the low solids bitumen extract. Potential benefits may include the production of smaller and more uniform agglomerates. The former may lead to higher bitumen recoveries and the latter may improve the solid-liquid separation rate. The bridging liquid may be added in an area of relatively high shear rates. Between stages of bridging liquid addition, agglomerates may be removed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Canadian patent applicationnumber 2,740,468 filed on May 18, 2011 entitled METHOD OF PROCESSING ABITUMINOUS FEED BY STAGED ADDITION OF A BRIDGING LIQUID, the entirety ofwhich is incorporated herein.

FIELD

The present disclosure relates generally to the field of hydrocarbonextraction from mineable deposits, such as bitumen from oil sands.

BACKGROUND

Methodologies for extracting hydrocarbon from oil sands have requiredenergy intensive processing steps to separate solids from the productshaving commercial value.

Solvent extraction processes for the recovery of the hydrocarbons havebeen proposed as an alternative to water extraction of oil sands.However, the commercial application of a solvent extraction process has,for various reasons, eluded the oil sands industry. A major challenge tothe application of solvent extraction to oil sands is the tendency offine particles within the oil sands to hamper the separation of solidsfrom the hydrocarbon extract. Solids agglomeration is a technique thatcan be used to deal with this challenge.

Solids agglomeration is a size enlargement technique that can be appliedwithin a liquid suspension to assist solid-liquid separation. Theprocess involves agglomerating fine solids, which are difficult toseparate from a liquid suspension, by the addition of a second liquid.The second liquid preferentially wets the solids but is immiscible withthe suspension liquid. With the addition of an appropriate amount of thesecond liquid and a suitable agitation; the second liquid displaces thesuspension liquid on the surface of the solids. As a result ofinterfacial forces between the three phases, the fines solidsconsolidate into larger, compact agglomerates that are more readilyseparated from the suspension liquid.

Solids agglomeration has been used in other applications to assistsolid-liquid separation. For example, the process has been used in thecoal industry to recover fine coal particles from the waste streamsproduced during wet cleaning treatments (see for example, U.S. Pat. No.3,856,668 (Shubert); U.S. Pat. No. 4,153,419 (Clayfield); U.S. Pat. No.4,209,301 (Nicol et al.); U.S. Pat. No. 4,415,445 (Hatem) and U.S. Pat.No. 4,726,810 (Ignasiak)). Solids agglomeration has also been proposedfor use in the solvent extraction of bitumen from oil sands. Thisapplication was coined Solvent Extraction Spherical Agglomeration(SESA). A more recent description of the SESA process can be found inSparks et al., Fuel 1992 (71); pp 1349-1353.

Previously described methodologies for SESA have not been commerciallyadopted. In general, the SESA process involves mixing oil sands with ahydrocarbon solvent, adding a bridging liquid to the oil sands slurry,agitating the mixture in a slow and controlled manner to nucleateparticles, and continuing such agitation to permit these nucleatedparticles to form larger multi-particle spherical agglomerates forremoval. The bridging liquid is preferably water or an aqueous solutionsince the solids of oil sands are mostly hydrophilic and water isimmiscible with hydrocarbon solvents.

The SESA process described by Meadus et al. in U.S. Pat. No. 4,057,486,involves combining solvent extraction with solids agglomeration toachieve dry tailings suitable for direct mine refill. In the process,organic material is separated from oil sands by mixing the oil sandsmaterial with an organic solvent to form a slurry, after which anaqueous bridging liquid is added in the amount of 8 to 50 wt % of thefeed mixture. By using controlled agitation, solid particles from oilsands come into contact with the aqueous bridging liquid and adhere toeach other to form macro-agglomerates of a mean diameter of 2 mm orgreater. The formed agglomerates are more easily separated from theorganic solvent compared to un-agglomerated solids. This processpermitted a significant decrease in water use, as compared withconventional water-based extraction processes. The multi-phase mixtureneed only be agitated severely enough and for sufficient time tointimately contact the aqueous liquid with the fine solids. The patentdiscloses that it is preferable that the type of agitation be a rollingor tumbling motion for at least the final stages of agglomeration. Thesetypes of motion should assist in forming compact and sphericalagglomerates from which most of the hydrocarbons are excluded. Theformed agglomerates are referred to as macro-agglomerates because theyresult from the consolidation of both the fine particles (sized lessthan 44 μm) and the coarse particles (sized greater than 200 μm) foundin the oil sands.

U.S. Pat. No. 3,984,287 (Meadus et al.) and U.S. Pat. No. 4,406,788(Meadus et al.) both describe apparatuses for extracting bitumen fromoil sands while forming macro-agglomerates for easy solid-liquidseparation. U.S. Pat. No. 3,984,287 (Meadus et al.) describes a twovessel agglomeration apparatus. The apparatus comprises a mixing vesselfor agitating the oil sands, the bridging liquid, and the solvent toform a slurry with suspended agglomerates. The slurry is screened inorder to remove a portion of the hydrocarbon liquid within with thebitumen product is dissolved. The agglomerates are then directed to atapered rotating drum where they are mixed with additional solvent andbridging liquid. The additional solvent acts to wash the excess bitumenfrom the agglomerates. The additional bridging liquid allows theagglomerates to grow by a layering mechanism and under the increasingcompressive forces produced by the tapered rotating drum bed depth. Thecompressive forces act to preferentially remove hydrocarbon liquid fromthe pores of the agglomerates such that, when optimal operatingconditions are imposed, the pores of the agglomerates end up beingfilled with only the bridging liquid, and the solvent that remains onthe surface of the agglomerates is easily recovered. U.S. Pat. No.4,406,788 (Meadus et al.) describes a similar apparatus to that of U.S.Pat. No. 3,984,287 (Meadus et al.), but where the extraction andagglomeration processes occurs within a single vessel. Within thisvessel, the flow of solvent is counter-current to the flow ofagglomerates which results in greater extraction efficiency.

The above mentioned patents describe methods of using the fines withinoil sands and an aqueous bridging liquid to promote the consolidation ofthe coarse oil sands particles into compact macro-agglomerates havingminimal entrained hydrocarbons and which are easily separated from thehydrocarbon liquid by simple screening. This macro-agglomeration processmay be suitable for oil sands feeds comprising greater than 15 wt %fines. For oil sands with a lesser amount of fines, the resultingagglomerates show poor strength and a significant amount of hydrocarbonsentrained within their pores. The inability of the macro-agglomerationprocess to produce agglomerates of similar solid-liquid separationcharacteristics regardless of oil sands feed grade, is a limitation.This limitation can be mitigated by using a water and fine particleslurry as the bridging liquid. U.S. Pat. No. 3,984,287 (Meadus et al.)reveals that middlings of a primary separation vessel of a water-basedextraction process or sludge from the water-based extraction tailingsponds may be used as the bridging liquids with high fines content. Ithas been shown that when sludge is used as the bridging liquid, theaddition of the same amount of sludge per unit weight of oil sands feedmay result in the production of agglomerates of the same drainageproperties regardless of oil sands quality. The use of sludge, however,introduces other challenges such as the fact that the appropriate sludgemay not be readily available at the mine site. Furthermore, the use ofsludge as the bridging liquid leads to larger agglomerates that are moreprone to entrapment of bitumen.

U.S. Pat. No. 4,719,008 (Sparks et al.) describes a process to addressthe agglomeration challenge posed by varying ore grades by means of amicro-agglomeration procedure in which the fine particles of the oilsands are consolidated to produce agglomerates with a similar particlesize distribution to the coarser grained particles of the oil sands.Using this micro-agglomeration procedure, the solid-liquid separationbehavior of the agglomerated oil sands will be similar regardless of oregrade. The micro-agglomeration process is described as occurring withina slowly rotating horizontal vessel. The conditions of the vessel favorthe formation of large agglomerates; however, a light milling action isused to continuously break down the agglomerates. The micro-agglomeratesare formed by obtaining an eventual equilibrium between cohesive anddestructive forces. Since rapid agglomeration and large agglomerates canlead to bitumen recovery losses owing to entrapment of extracted bitumenwithin the agglomerated solids, the level of bridging liquid is kept aslow as possible commensurate with achieving economically viablesolid-liquid separation.

The micro-agglomeration process described in U.S. Pat. No. 4,719,008(Sparks et al.) has several disadvantages that have thus far limited theapplication of the technology. Some of these disadvantages will now bedescribed.

The micro-agglomeration process described in U.S. Pat. No. 4,719,008(Sparks et al.) requires careful control of the bridging liquid tosolids ratio. If the amount of bridging liquid added to the process isin excess of the required amount, rapid growth of agglomerates can leadto bitumen recovery losses owing to entrapment of bitumen within theagglomerated solids. However, if the amount of bridging liquid added tothe process is too low, insufficient agglomeration increases the amountof dispersed fines in the liquid suspension which hampers solids-liquidseparation. In U.S. Pat. No. 4,719,008 (Sparks et al.) a ratio between0.112 and 0.12 was identified as an appropriate range for bridgingliquid to solids ratio for a particular type of low grade ore.Maintaining the ratio within a narrow range during the actual fieldoperation of the agglomeration process would be a challenge.Furthermore, the desired amount of bridging liquid for the agglomerationprocess will depend on the ore quality and the chemistry of the fines.Because the ore quality and chemistry will change on a frequent basis asdifferent mine shelves are progressed, the recipe of the agglomerationprocess may need to change accordingly in order to maintain theagglomeration output within an acceptable range.

In previously described SESA processes, the bridging liquid is eitheradded directly to the dry oil sands or it is added to the oil sandsslurry comprising the oil sands and the hydrocarbon solvent. In theformer scenario, bitumen extraction and particle agglomeration occurssimultaneously. For this reason, the growth of agglomerates may hamperthe dissolution of the bitumen into the solvent, it may lead to trappingof bitumen within the agglomerates, and it may result in an overallincrease in the required residence time for bitumen extraction. In thescenario where the bridging liquid is added to the oil sands slurry,excessive agglomeration may occur in the locations of bridging liquidinjection. These agglomerates will tend to be larger than the desiredagglomerate size and result in an increase in the viscosity of theslurry. A higher slurry viscosity may hamper the mixing needed touniformly distribute the bridging liquid throughout the remaining areasof the slurry. Poor bridging liquid dispersion may result in a largeagglomerate size distribution, which is not preferred.

An important step in the agglomeration process is the distribution ofthe bridging liquid throughout the liquid suspension. Poor distributionof the bridging liquid may result in regions within the slurry of toolow and too high binging liquid concentrations. Regions of low bridgingliquid concentrations may have no or poor agglomeration of fine solids,which may result in poor solid-liquid separation. Regions of highbridging liquid concentration may have excess agglomeration of solids,which may result in the trapping of bitumen or bitumen extract withinthe large agglomerates. In the process described in U.S. Pat. No.4,719,008 (Sparks et al.), the milling action of the rotating vesselacts to both breakup large agglomerates and distribute the bridgingliquid throughout the vessel in order to achieve uniform agglomerateformation. In a commercial application, the rotating vessel would needto be large enough to process the high volumetric flow rates of oilsands. Accomplishing uniform mixing of the bridging liquid in such alarge vessel would require a significant amount of mixing energy andlong residence times.

Coal mining processes often produce aqueous slurries comprising finecoal particles. Solids agglomeration has been proposed as a method ofrecovering these fine coal particles, which may constitute up to 30 wt.% of the mined coal. In the solids agglomeration process, thehydrophobic coal particles are agglomerated within the aqueous slurry byadding an oil phase as the bridging liquid. When the aqueous slurry,with bridging liquid, is agitated, the coal particles become wetted withan oil layer and adhere to each other to form agglomerates. Thehydrophilic ash particles are not preferentially wetted by the oil phaseand, as a result, remain un-agglomerated and suspended in the aqueousphase. The agglomerated coal material, with reduced ash content, isreadily separated from the aqueous slurry by mechanical methods such asscreening.

U.S. Pat. No. 4,153,419 (Clayfield et al.) describes a process for theagglomeration of coal fines within an aqueous slurry by staged additionof a bridging liquid to the aqueous slurry. Each agglomeration stagecomprises the addition of a bridging liquid to the slurry, agitation ofthe mixture, and removal of agglomerates from the aqueous slurry. Theinventors found that performing the agglomeration process in at leasttwo stages yielded higher agglomeration of the coal particles ascompared to the case where the same amount of bridging liquid was addedin one agglomeration stage.

U.S. Pat. No. 4,415,445 (Van Hattem et al.) describes a process for theagglomeration of coal fines within an aqueous slurry by the addition ofa bridging liquid and the addition of seed pellets that aresubstantially larger than the coal fines. The presence of seed pelletsinduces agglomerate growth to occur predominately by a layeringmechanism rather than by a coalescence mechanism. Since the rate ofagglomeration occurs much faster by layering compared to coalescence,the process described therein allows agglomerates to form very quicklyso that, for a given residence time, a higher throughput of agglomeratescan be obtained compared to the throughput obtainable in the absence ofseed pellets.

It would be desirable to provide an alternative or improved method forprocessing a bituminous feed.

SUMMARY

The present disclosure relates to a method of processing a bituminousfeed. The bituminous feed is contacted with an extraction liquor to forma slurry. A bridging liquid is added to the slurry in at least twostages and solids within the slurry are agitated to form an agglomeratedslurry comprising agglomerated solids and a low solids bitumen extract.The bridging liquid is added to the slurry in regions having highershear rates than a median shear rate within the slurry. The agglomeratesare then separated from the low solids bitumen extract. Potentialbenefits may include the production of smaller and more uniformagglomerates. The former may lead to higher bitumen recoveries and thelatter may improve the solid-liquid separation rate.

In a first aspect, the present disclosure provides a method ofprocessing a bituminous feed, the method comprising: a) contacting thebituminous feed with an extraction liquor to form a slurry, wherein theextraction liquor comprises a solvent; b) adding a bridging liquid tothe slurry in at least two stages and agitating solids within the slurryto form an agglomerated slurry comprising agglomerates and a low solidsbitumen extract; said bridging liquid being added to the slurry inregions having higher shear rates than a median shear rate within theslurry; and c) separating the agglomerates from the low solids bitumenextract.

Other aspects and features of the present disclosure will becomeapparent to those ordinarily skilled in the art upon review of thefollowing description of specific embodiments in conjunction with theaccompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described, by way ofexample only, with reference to the attached Figures.

FIG. 1 is a flow chart illustrating a disclosed embodiment.

FIG. 2 is a schematic illustrating a disclosed embodiment.

FIG. 3 is a schematic illustrating a disclosed embodiment.

FIG. 4 is a schematic illustrating a disclosed embodiment.

FIG. 5 is a schematic illustrating a disclosed embodiment.

FIG. 6 is a schematic illustrating a disclosed embodiment.

DETAILED DESCRIPTION

The present disclosure relates to a method of processing a bituminousfeed using staged addition of a bridging liquid. This method may becombined with aspects of other solvent extraction processes, includingbut not limited to those described above in the background section, andthose described in Canadian Patent Application Serial No. 2,724,806(“Adeyinka et al.”), filed Dec. 10, 2010 and entitled “Processes andSystems for Solvent Extraction of Bitumen from Oil Sands”.

Prior to describing embodiments specifically related to the stagedaddition of bridging liquid, a summary of the processes described inAdeyinka et al. will now be provided.

Summary of Processes of Solvent Extraction Described in Adeyinka et al.

To extract bitumen from oil sands in a manner that employs solvent, asolvent is combined with a bituminous feed derived from oil sand to forman initial slurry. Separation of the initial slurry into a fine solidsstream and coarse solids stream may be followed by agglomeration ofsolids from the fine solids stream to form an agglomerated slurry. Theagglomerated slurry can be separated into agglomerates and a low solidsbitumen extract. Optionally, the coarse solids stream may bereintroduced and further extracted in the agglomerated slurry. A lowsolids bitumen extract can be separated from the agglomerated slurry forfurther processing. Optionally, the mixing of a second solvent with thelow solids bitumen extract to extract bitumen may take place, forming asolvent-bitumen low solids mixture, which can then be separated furtherinto low grade and high grade bitumen extracts. Recovery of solvent fromthe low grade and/or high grade extracts is conducted, to producebitumen products of commercial value.

Staged Addition of Bridging Liquid

As outlined in the summary section, and now with reference to FIG. 1,the present disclosure relates to a method of processing a bituminousfeed. The bituminous feed is contacted with an extraction liquor to forma slurry (102). A bridging liquid is added to the slurry in at least twostages and solids within the slurry are agitated to form an agglomeratedslurry comprising agglomerated solids and a low solids bitumen extract(104). The bridging liquid is added to the slurry in regions havinghigher shear rates than a median shear rate within the slurry. Theagglomerates are then separated from the low solids bitumen extract(106). Potential benefits may include the production of smaller and moreuniform agglomerates. The former may lead to higher bitumen recoveriesand the latter may improve the solid-liquid separation rate.

The term “bituminous feed” refers to a stream derived from oil sandsthat requires downstream processing in order to realize valuable bitumenproducts or fractions. The bituminous feed is one that comprises bitumenalong with undesirable components. Such a bituminous feed may be deriveddirectly from oil sands, and may be, for example raw oil sands ore.Further, the bituminous feed may be a feed that has already realizedsome initial processing but nevertheless requires further processing.Also, recycled streams that comprise bitumen in combination with othercomponents for removal as described herein can be included in thebituminous feed. A bituminous feed need not be derived directly from oilsands, but may arise from other processes. For example, a waste productfrom other extraction processes which comprises bitumen that wouldotherwise not have been recovered, may be used as a bituminous feed.Such a bituminous feed may be also derived directly from oil shale oil,bearing diatomite or oil saturated sandstones.

As used herein, “agglomerate” refers to conditions that produce acluster, aggregate, collection or mass, such as nucleation, coalescence,layering, sticking, clumping, fusing and sintering, as examples.

FIG. 2 is a schematic of a disclosed embodiment with additional stepsincluding downstream solvent recovery. The extraction liquor (202) ismixed with a bituminous feed (204) from oil sands in a slurry system(206) to form a slurry (208). The extraction liquor comprises a solventand is used to extract bitumen from the bituminous feed. The slurry isfed into an agglomerator (210). Extraction may begin when the extractionliquor (202) is contacted with the bituminous feed (204) and a portionof the extraction may occur in the agglomerator (210). A bridging liquid(212) is added to the agglomerator (210) to assist agglomeration of theslurry. Some form of agitation is also used to assist agglomeration asdescribed below.

The agglomerated slurry (214), comprising agglomerates and a low solidsbitumen extract, is sent to a solid-liquid separator (216) to produce alow solids bitumen extract (218) and agglomerates (220).

The following additional steps may also be performed. The low solidsbitumen extract (218) is sent to a solvent recovery unit (222) torecover solvent (224) leaving a bitumen product (226). The agglomerates(220) are sent to a tailings solvent recovery unit (228) to recoversolvent (230) leaving dry tailings (232).

In one embodiment, the bituminous feed is dry oil sands, which iscontacted with extraction liquor that free of bridging liquid in aslurry system to produce a pumpable slurry. The slurry may be well mixedin order to dissolve the bitumen. The bridging liquid is then added tothe slurry in order to agglomerate the fine solids within the slurry.The rate of agglomeration may be controlled by a balance amongagitation, fines content of the slurry, and bridging liquid addition. Inthis embodiment, the bitumen is first extracted from the bituminous feedprior to agglomeration in order to prevent (or limit) the agglomerationprocess from hampering the dissolution of bitumen into the extractionliquor.

In one embodiment, the formed agglomerates are sized on the order of0.1-1.0 mm, or on the order of 0.1-0.3 mm. In one embodiment, at least80 wt. % of the formed agglomerates are 0.1-1.0 mm or 0.1 to 0.3 mm insize.

FIG. 3 illustrates an embodiment where the bridging liquid is added toan agglomeration vessel at multiple locations within the vessel. Asillustrated, the bituminous feed (302) is added to an agglomerator(304). Bridging liquid (306) is added at multiple stages along the flowpath of the slurry. For example, multiple bridging liquid inlet portsmay be arranged sequentially along the agglomerator. The agglomeratedslurry (308) is also shown.

After each stage of bridging liquid addition, the slurry may be wellagitated so that the bridging liquid comes into contact with the solidswithin the slurry in order to form agglomerates. In one embodiment, theresidence time between each stage of bridging liquid addition issufficient to allow agglomeration of some of the fine particles withinthe slurry. The residence time between each stage of bridging liquidaddition may be greater than 30 seconds.

After each stage of bridging liquid addition and the resulting formationof agglomerates, the formed agglomerates may be removed from the slurry.Exemplary methods for removing the agglomerates include gravityseparation or screening within the agglomerator. Agglomerates that arelarger than 1 mm are typically undesirable due to the increased chanceof bitumen entrapment within the large agglomerates. These largeagglomerates that are removed from the agglomerator may be separatelycomminuted by various methods known in the art to obtain agglomerates ofthe preferred size. For example, the agglomerates may be comminutedwithin attrition scrubbers or rod mills.

In one embodiment, the bridging liquid is added to the slurry atrelatively high agitation or mixing energy regions in order to improvethe dispersion of the bridging liquid within the slurry. Therefore, thebridging liquid may be added to the slurry in regions having highershear rates than a median shear rate within the slurry. An example of aregion of high shear rate within an agglomerator is adjacent thepropellers of a mixing vessel such as an attrition scrubber. Thepropellers themselves may contain suitable injection ports designed forinjecting bridging liquid, at high shear, into the slurry. In anotherexample, the bridging liquid may be added to the slurry within the pumpsused to transport the slurry.

The staged addition of bridging liquid may be used to assist in moreuniformly agglomerating solids. The amount of bridging liquid added ateach stage of bridging liquid addition may be selected to obtain thedesired agglomerate size.

FIG. 4 illustrates an embodiment where the bridging liquid is added toan agglomeration vessel “continuously”. As illustrated, the bituminousfeed (402) is added to an agglomerator (404). Bridging liquid (406) isadded “continuously” along the flow path of the slurry. As used herein“continuously” means that the bridging liquid is added at stagesseparated by residence times that are significantly shorter than theresidence time needed for agglomerate formation. For examples, theresidence times between each bridging liquid stage may be less than 15seconds, or less than 5 seconds. The agglomerated slurry (408) is alsoshown.

FIG. 5 illustrates an embodiment where the bridging liquid is added tomultiple agglomerators. As illustrated, the bituminous feed (502) isadded to a first agglomerator (504 a), to which bridging liquid (506 a)is added. The slurry (503 a) exists the first agglomerator (504 a) andenters the second agglomerator (504 b), to which bridging liquid (506 b)is added. The slurry (503 b) exists the second agglomerator (504 b) andenters the third agglomerator (504 c), to which bridging liquid (506 c)is added. The agglomerated slurry (508) is also shown. The use ofmultiple agglomerators allows for distinct stages of agglomeration tooccur within each vessel. For example, one agglomerator may be used forthe initial nucleation of agglomerate particles. A second agglomeratormay be used to grow the agglomerates. A third agglomerator may be usedfor comminution of agglomerates. Since these stages of agglomeration mayoccur in separate vessels, the operator may have a greater level ofcontrol of the processes.

FIG. 6 illustrates an embodiment where agglomerates are removed from theslurry after they form and before the injection of additional bridgingliquid. As illustrated, the bituminous feed (602) is added to a firstagglomerator (604 x), to which bridging liquid (606 x) is added. Theslurry (610) exists the first agglomerator (604 x) and enters asolid-liquid separator (612) (examples of which are described below)separating agglomerates (614) from the reduced-solids slurry (616). Thereduced-solids slurry (616) is fed into the second agglomerator (604 y),to which bridging liquid (606 y) is added. The agglomerated slurry (608)is also shown. More than two agglomerators and more than onesolid-liquid separator could be used.

Exemplary methods for removing the agglomerates include, but are notlimited to, gravity separators such as thickeners or enhanced gravityseparators such as hydrocyclones. The agglomerates may be removed fromthe slurry in order to reduce their additional growth. It has been shownin previous studies that in order to maximize bitumen recovery, it isdesirable to keep the agglomerates average particle size to as low avalue as possible commensurate with achieving economically viable solidliquid separation. If the agglomerates were to remain within the slurry,after subsequent bridging liquid additions, un-agglomerated fineparticles would preferentially attach to the agglomerates, thusincreasing the chances of bitumen entrapment within the growingagglomerates. Additionally, a portion of the agglomerates that areremoved from the agglomerators may be separately comminuted by variousmethods known in the art to obtain agglomerates of the preferred size.For example, the agglomerates may be comminuted within attritionscrubbers or rod mills.

The agglomeration processes herein described may be used for theformation of macro-agglomerates or micro-agglomerates from the solids ofthe bituminous feed. Macro-agglomerates are agglomerates that arepredominantly greater than 2 mm in diameter. These agglomerates compriseboth the fine particles (less than 44 μm) and sand grains of the oilsands. Micro-agglomerates are agglomerates that are predominately lessthan 1 mm in diameter and they principally comprise fine particles ofthe oil sands. It has been found that for the SESA process describedabove, the formation of micro-agglomerates are more suitable formaximizing bitumen recovery for a range of oil sands grades.

Agitation

Agglomeration is assisted by some form of agitation. The form ofagitation may be mixing, shaking, rolling, or another known suitablemethod. The agitation of the feed need only be severe enough and ofsufficient duration to intimately contact the bridging liquid with thesolids in the feed. Exemplary rolling type vessels include rod mills andtumblers. Exemplary mixing type vessels include mixing tanks, blenders,and attrition scrubbers. In the case of mixing type vessels, asufficient amount of agitation is needed to keep the formed agglomeratesin suspension. In rolling type vessels, the solids content of the feedis, in one embodiment, greater than 40 wt. % so that compaction forcesassist agglomerate formation.

Extraction Liquor

The extraction liquor comprises a solvent used to extract bitumen fromthe bituminous feed. The term “solvent” as used herein should beunderstood to mean either a single solvent, or a combination ofsolvents.

In one embodiment, the extraction liquor comprises a hydrocarbon solventcapable of dissolving the bitumen. The extraction liquor may be asolution of a hydrocarbon solvent(s) and bitumen, where the bitumencontent of the extraction liquor may range between 10 to 50 wt %. It maybe desirable to have dissolved bitumen within the extraction liquor inorder to increase the volume of the extraction liquor without anincrease in the required inventory of hydrocarbon solvent(s). In caseswhere non-aromatic hydrocarbon solvents are used, the dissolved bitumenwithin the extraction liquor also increases the solubility of theextraction liquor towards dissolving additional bitumen.

The extraction liquor may be mixed with the bituminous feed to form aslurry where most or all of the bitumen from the oil sands is dissolvedinto the extraction liquor. In one embodiment, the solids content of theslurry is in the range of 10 wt % to 75 wt %, or 50 to 65 wt %. A slurrywith a higher solids content may be more suitable for agglomeration in arolling type vessels, where the compressive forces aid in the formationof compact agglomerates. For turbulent flow type vessels, such as anattrition scrubber, a slurry with a lower solids content may be moresuitable.

The solvent used in the process may include low boiling point solventssuch as low boiling point cycloalkanes, or a mixture of suchcycloalkanes, which substantially dissolve asphaltenes. The solvent maycomprise a paraffinic solvent in which the solvent to bitumen ratio ismaintained at a level to avoid or limit precipitation of asphaltenes.

While it is not necessary to use a low boiling point solvent, when it isused, there is the extra advantage that solvent recovery through anevaporative process proceeds at lower temperatures, and requires a lowerenergy consumption. When a low boiling point solvent is selected, it maybe one having a boiling point of less than 100° C.

The solvent selected according to certain embodiments may comprise anorganic solvent or a mixture of organic solvents. For example, thesolvent may comprise a paraffinic solvent, an open chain aliphatichydrocarbon, a cyclic aliphatic hydrocarbon, or a mixture thereof.Should a paraffinic solvent be utilized, it may comprise an alkane, anatural gas condensate, a distillate from a fractionation unit (ordiluent cut), or a combination of these containing more than 40% smallchain paraffins of 5 to 10 carbon atoms. These embodiments would beconsidered primarily a small chain (or short chain) paraffin mixture.Should an alkane be selected as the solvent, the alkane may comprise anormal alkane, an iso-alkane, or a combination thereof. The alkane mayspecifically comprise heptane, iso-heptane, hexane, iso-hexane, pentane,iso-pentane, or a combination thereof. Should a cyclic aliphatichydrocarbon be selected as the solvent, it may comprise a cycloalkane of4 to 9 carbon atoms. A mixture of C₄-C₉ cyclic and/or open chainaliphatic solvents would be appropriate.

Exemplary cycloalkanes include cyclohexane, cyclopentane, or a mixturethereof.

If the solvent is selected as the distillate from a fractionation unit,it may for example be one having a final boiling point of less than 180°C. An exemplary upper limit of the final boiling point of the distillatemay be less than 100° C.

A mixture of C₄-C₁₀ cyclic and/or open chain aliphatic solvents wouldalso be appropriate. For example, it can be a mixture of C₄-C₉ cyclicaliphatic hydrocarbons and paraffinic solvents where the percentage ofthe cyclic aliphatic hydrocarbon in the mixture is greater than 50%.

Extraction liquor may be recycled from a downstream step. For instance,as described below, solvent recovered in a solvent recovery unit, may beused to wash agglomerates, and the resulting stream may be used asextraction liquor. As a result, the extraction liquor may compriseresidual bitumen and residual solid fines.

The solvent may also include additives. These additives may or may notbe considered a solvent per se. Possible additives may be componentssuch as de-emulsifying agents or solids aggregating agents. Having anagglomerating agent additive present in the bridging liquid anddispersed in the first solvent may be helpful in the subsequentagglomeration step. Exemplary agglomerating agent additives includedcements, fly ash, gypsum, lime, brine, water softening wastes (e.g.magnesium oxide and calcium carbonate), solids conditioning andanti-erosion aids such as polyvinyl acetate emulsion, commercialfertilizer, humic substances (e.g. fulvic acid), polyacrylamide basedflocculants and others. Additives may also be added prior to gravityseparation with the second solvent to enhance removal of suspendedsolids and prevent emulsification of the two solvents. Exemplaryadditives include methanoic acid, ethylcellulose and polyoxyalkylateblock polymers.

Bridging Liquid

A bridging liquid is a liquid with affinity for the solids particles inthe bituminous feed, and which is immiscible in the solvent. Exemplaryaqueous liquids may be recycled water from other aspects or steps of oilsands processing. The aqueous liquid need not be pure water, and mayindeed be water containing one or more salt, a waste product fromconventional aqueous oil sand extraction processes which may includeadditives, aqueous solution with a range of pH, or any other acceptableaqueous solution capable of adhering to solid particles within anagglomerator in such a way that permits fines to adhere to each other.An exemplary bridging liquid is water.

The total amount of bridging liquid added to the slurry may be such thata ratio of bridging liquid to solids within the agglomerated slurry isin the range of 0.02 to 0.25, or 0.05 and 0.11. The amount of bridgingliquid that makes up this ratio includes the bridging liquid added tothe slurry and the connate water from the bituminous feed. The amount ofbridging liquid that is added at a stage may be the same for each stage,or may be different.

In one embodiment, the bridging liquid may contain fine particles (sizedless than 44 μm) suspended therein. These fine particles may serve asseed particles for the agglomeration process. In one embodiment, thebridging liquid has a solids content of less than 40 wt. %. In oneembodiment, the agglomerated slurry has a solids content of 20 to 70 wt.%.

The composition of the bridging liquid, for example salinity and/orfines content, may be the same or different depending on which stagealong the along the slurry flow path the bridging liquid is added.Additionally, the amount of the bridging liquid that is added to theslurry at each stage of bridging liquid addition may be the same ordifferent. For example, the bridging liquid added during a first stagemay have a salinity that is at least 10% higher or lower than a salinityof a bridging liquid added during a second, subsequent stage. In anotherexamples, the bridging liquid added during a first stage may have asuspended solids content that is at least 10% higher or lower than asuspended solids content of a bridging liquid added during a second,subsequent stage.

General Experimental Observations

Preliminary batch tests of solvent extraction have shown that bitumenrecovery increased by as much as five percentage points when thebridging liquid was added into the process vessel at intermittent timeintervals during the agglomeration process compared to the case whereall the bridging liquid was added at the beginning of the agglomerationprocess. The improved bitumen recovery performance demonstrated by thestaged bridging liquid addition is also supported by observations madeduring batch testing of the solids agglomeration process within a mixingvessel. In these tests, a translucent organic fluid was used as thecontinuous phase with sand and clay as the solids, and water as thebridging liquid. When the water was added all at once to the slurrycomprising the organic fluid and solids, large agglomerates quicklyformed and began to segregate from the slurry. The slurry remainedsegregated until sufficient mixing energy was applied to the slurry tobreak up the initially formed agglomerates and disperse the water. Theparticle size distribution of the agglomerates formed in this suboptimalcase was found to be broad with a significant amount of agglomeratesbeing outside the size range for optimal bitumen recovery andsolid-liquid separation. For the tests where the water was addedgradually and near the mixing impellers for increased mixing energy, thewater rapidly dispersed and minimal segregation of agglomerates wasobserved. The particles size distribution of these agglomerates wasfound to be narrow, and as a result the bridging liquid can be used moreefficiently to obtain the desired agglomerate size.

Ratio of Solvent to Bitumen for Agglomeration

The process may be adjusted to render the ratio of the solvent tobitumen in the agglomerator at a level that avoids precipitation ofasphaltenes during agglomeration. Some amount of asphalteneprecipitation is unavoidable, but by adjusting the amount of solventflowing into the system, with respect to the expected amount of bitumenin the bituminous feed, when taken together with the amount of bitumenthat may be entrained in the extraction liquor used, can permit thecontrol of a ratio of solvent to bitumen in the agglomerator. When thesolvent is assessed for an optimal ratio of solvent to bitumen duringagglomeration, the precipitation of asphaltenes can be minimized oravoided beyond an unavoidable amount. Another advantage of selecting anoptimal solvent to bitumen ratio is that when the ratio of solvent tobitumen is too high, costs of the process may be increased due toincreased solvent requirements.

An exemplary ratio of solvent to bitumen to be selected as a targetratio during agglomeration is less than 2:1. A ratio of 1.5:1 or less,and a ratio of 1:1 or less, for example, a ratio of 0.75:1, would alsobe considered acceptable target ratios for agglomeration. For clarity,ratios may be expressed herein using a colon between two values, such as“2:1”, or may equally be expressed as a single number, such as “2”,which carries the assumption that the denominator of the ratio is 1 andis expressed on a weight to weight basis.

Slurry System

The slurry system may optionally be a mix box, a pump, or a combinationof these. By slurrying the extraction liquor together with thebituminous feed, and optionally with additional additives, the bitumenentrained within the feed is given an opportunity to become extractedinto the solvent phase prior to agglomeration within the agglomerator.

Solid-Liquid Separator

As described above, the agglomerated slurry may be separated into a lowsolids bitumen extract and agglomerates in a solid-liquid separator. Thesolid-liquid separator may comprise any type of unit capable ofseparating solids from liquids, so as to remove agglomerates. Exemplarytypes of units include a gravity separator, a clarifier, a cyclone, ascreen, a belt filter or a combination thereof.

The system may contain a solid-liquid separator but may alternativelycontain more than one. When more than one solid-liquid separation stepis employed at this stage of the process, it may be said that both stepsare conducted within one solid-liquid separator, or if such steps aredissimilar, or not proximal to each other, it may be said that a primarysolid-liquid separator is employed together with a secondarysolid-liquid separator. When primary and secondary units are bothemployed, generally, the primary unit separates agglomerates, while thesecondary unit involves washing agglomerates.

Non-limiting methods of solid-liquid separation of an agglomeratedslurry are described in Canadian Patent Application Serial No. 2,724,806(Adeyinka et al.), filed Dec. 10, 2010.

Secondary Stage of Solid-Liquid Separation to Wash Agglomerates

As a component of the solid-liquid separator, a secondary stage ofseparation may be introduced for countercurrently washing theagglomerates separated from the agglomerated slurry. The initialseparation of agglomerates may be said to occur in a primarysolid-liquid separator, while the secondary stage may occur within theprimary unit, or may be conducted completely separately in a secondarysolid-liquid separator. By “countercurrently washing”, it is meant thata progressively cleaner solvent is used to wash bitumen from theagglomerates. Solvent involved in the final wash of agglomerates may bere-used for one or more upstream washes of agglomerates, so that themore bitumen entrained on the agglomerates, the less clean will be thesolvent used to wash agglomerates at that stage. The result being thatthe cleanest wash of agglomerates is conducted using the cleanestsolvent.

A secondary solid-liquid separator for countercurrently washingagglomerates may be included in the system or may be included as acomponent of a system described herein. The secondary solid-liquidseparator may be separate or incorporated within the primarysolid-liquid separator. The secondary solid-liquid separator mayoptionally be a gravity separator, a cyclone, a screen or belt filter.Further, a secondary solvent recovery unit for recovering solventarising from the solid-liquid separator can be included. The secondarysolvent recovery unit may be conventional fractionation tower or adistillation unit.

When conducted in the process, the secondary stage for countercurrentlywashing the agglomerates may comprise a gravity separator, a cyclone, ascreen, a belt filter, or a combination thereof.

The solvent used for washing the agglomerates may be solvent recoveredfrom the low solids bitumen extract, as described with reference toFIGS. 2 to 4. A second solvent may alternatively or additionally be usedas described in Canadian Patent Application Serial No. 2,724,806(Adeyinka et al.) for additional bitumen extraction downstream of theagglomerator.

Recycle and Recovery of Solvent

The process may involve removal and recovery of solvent used in theprocess.

In this way, solvent is used and re-used, even when a good deal ofbitumen is entrained therein. Because an exemplary solvent:bitumen ratioin the agglomerator may be 2:1 or lower, it is acceptable to userecycled solvent containing bitumen to achieve this ratio. The amount ofmake-up solvent required for the process may depend solely on solventlosses, as there is no requirement to store and/or not re-use solventthat have been used in a previous extraction step. When solvent is saidto be “removed”, or “recovered”, this does not require removal orrecovery of all solvent, as it is understood that some solvent will beretained with the bitumen even when the majority of the solvent isremoved.

The system may contain a single solvent recovery unit for recovering thesolvent(s) arising from the gravity separator. The system mayalternatively contain more than one solvent recovery unit.

Solvent may be recovered by conventional means. For example, typicalsolvent recovery units may comprise a fractionation tower or adistillation unit. The solvent recovered in this fashion will notcontain bitumen entrained therein. This clean solvent is preferably usedin the last wash stage of the agglomerate washing process in order thatthe cleanest wash of the agglomerates is conducted using the cleanestsolvent.

The solvent recovered in the process may comprise entrained bitumentherein, and can thus be re-used as the extraction liquor for combiningwith the bituminous feed. Other optional steps of the process mayincorporate the solvent having bitumen entrained therein, for example incountercurrent washing of agglomerates, or for adjusting the solvent andbitumen content prior to agglomeration to achieve the selected ratiowithin the agglomerator that avoids precipitation of asphaltenes.

Extraction Step May be Separate from Agglomeration Step

Solvent extraction may be conducted separately from agglomeration incertain embodiments of the process. Unlike certain prior processes,where the solvent is first exposed to the bituminous feed within theagglomerator, certain embodiments described herein include contact ofthe extraction liquor with the bituminous feed prior to theagglomeration step. This has the effect of reducing residence time inthe agglomerator, when compared to certain previously proposed processeswhich require extraction of bitumen and agglomeration to occursimultaneously. The instant process is tantamount to agglomeration ofpre-blended slurry in which extraction via bitumen dissolution issubstantially or completely achieved separately. Performing extractionupstream of the agglomerator permits the use of enhanced materialhandling schemes whereby flow/mixing systems such as pumps, mix boxes orother types of conditioning systems can be employed. Additionally,performing extraction upstream of the agglomerator prevents theagglomeration process from hampering the dissolution of bitumen into theextraction liquor.

Because the extraction may occur upstream of the agglomeration step, theresidence time in the agglomerator may be reduced. One other reason forthis reduction is that by adding components, such as water, some initialnucleation of particles that ultimately form larger agglomerates canoccur prior to the agglomerator.

Dilution of Agglomerator Discharge to Improve Product Quality

Solvent may be added to the agglomerated slurry for dilution of theslurry before discharge into the primary solid-liquid separator, whichmay be for example a deep cone settler. This dilution can be carried outin a staged manner to pre-condition the primary solid-liquid separatorfeed to promote higher solids settling rates and lower solids content inthe solid-liquid separator's overflow. The solvent with which the slurryis diluted may be derived from recycled liquids from the liquid-solidseparation stage or from other sources within the process.

When dilution of agglomerator discharge is employed in this embodiment,the solvent to bitumen ratio of the feed into the agglomerator is set toobtain from about 10 to about 90 wt % bitumen in the discharge, and aworkable viscosity at a given temperature. In certain cases, theseviscosities may not be optimal for the solid-liquid separation (orsettling) step. In such an instance, a dilution solvent of equal orlower viscosity may be added to enhance the separation of theagglomerated solids in the clarifier, while improving the quality of theclarifier overflow by reducing viscosity to permit more solids tosettle. Thus, dilution of agglomerator discharge may involve adding thesolvent, or a separate dilution solvent, which may, for example,comprise an alkane.

Potential Advantages

There may be advantages of embodiments described herein, for instance ascompared to SESA. It is believed that adding the bridging liquid atmultiple stages along the flow path of oil sands slurry can lead to anagglomeration process that is more controllable and yield agglomeratesof more uniform size. It is also believed that adding the bridgingliquid at multiple stages along the flow path of oil sands slurry willreduce the overall energy requirement of the agglomeration process.Similar advantages have been realized in the agglomeration of coal fineparticles (see U.S. Pat. No. 4,153,419).

The high energy requirements of solids agglomeration process is a wellknown limitation. Embodiments described herein are expected to reducethe total energy needed to form the agglomerates. The reduction inenergy is due to the lower power requirement needed for theagglomeration process. The reduction in power, in turn, is due to thestaged addition of bridging liquid. Since the bridging liquid is addedin stages, the viscosity of the oil sands does not increase as much asit would if all the bridging liquid was added at once. A reduction inthe power requirement means that that the torque requirements of motorsused in certain types of agglomeration vessel can be reduced. In thecase of rotating type vessels, the required amount of milling can bereduced. Furthermore, the wear of the internals of the vessels will bedramatically reduced due to a reduction in the required mixingintensity.

Without intending to be bound by theory, it is believed that stagedaddition of bridging liquid helps balance the rate of agglomeration withthe rate of mixing. In the presence of a significant amount of bridgingliquid, the agglomeration of the solids occur at a rate that is muchmore rapid than the rate of mixing of the slurry. In fact, theagglomeration process itself tends to hamper mixing by increasing theeffective viscosity of the slurry. The staged addition of the bridgingliquid may modulate the rate of agglomeration at any particular locationin the vessel. Thus, the mixing of the slurry can match theagglomeration process to ensure that the slurry remains relativelyhomogeneous. The addition of bridging liquid in high mixing energyregions of the slurry assist bridging liquid dispersion throughout theslurry. Additionally, removing the agglomerates from the slurry aftereach stage of bridging liquid addition reduces the viscosity of theslurry and prevents (or limits) excessive growth of the formedagglomerates.

Another potential advantage of certain embodiments is the shifting ofthe growth of agglomerates to a layering mechanism rather than acoalescence mechanism. The layering mechanism refers to agglomerategrowth where the individual fine particles stick on the surface ofalready formed agglomerates. The coalescence mechanism refersagglomerate growth where two or more agglomerates stick together. Thelayering mechanism should result in more compact agglomerates with lessbitumen extract entrapped therein. In the cases where the formedagglomerates remain in the slurry, these agglomerates act as seedparticles and shift the agglomeration process to more of a layeringmechanism than a coalescence mechanism, which may dominate theagglomerate growth mechanism if all the bridging liquid was introducedin a single stage.

In the preceding description, for purposes of explanation, numerousdetails are set forth in order to provide a thorough understanding ofthe embodiments. However, it will be apparent to one skilled in the artthat these specific details are not required.

The above-described embodiments are intended to be examples only.Alterations, modifications and variations can be effected to theparticular embodiments by those of skill in the art without departingfrom the scope, which is defined solely by the claims appended hereto.

Batch Experiments

Experiments were conducted to test the effectiveness of using stagedaddition of bridging liquid in order to agglomerate oil sand solidswithin a slurry. The initial liquid drainage rate of the formedagglomerates and bitumen recovery from the oil sands were used as theexperimental measurements to determine the effectiveness of the solventextraction with agglomeration process. The agglomerates were alsovisually inspected for their size and uniformity.

Medium grade Athabasca oil sand was used in these experiments. The oilsands had a bitumen content of 9.36 wt % and a water content of 4.66 wt%. The percentage of fines (<44 μm) that make up the solids wasapproximately 25 wt %. The oil sands were kept at −20° C. until theywere ready for use. A solution of cyclohexane and bitumen was used asthe extraction liquor. The percentage of bitumen in the extractionliquor was 24 wt %. Distilled water was used as the bridging liquid. Foreach experiment a total of 350 g of oil sands, 235.07 g of extractionliquor, and a total of 16.8 g of water were used. This compositiontranslated to a solids content of 50 wt % and a water to solids ratio of0.11 for the agglomerated slurry.

A Parr reactor (series 5100) (Parr Instrument Company, Moline, Ill.,USA) was used as the extractor and agglomerator. The reactor vessel wasmade of glass that permits direct observation of the mixing process. Aturbine type impeller powered by an explosion proof motor of 0.25 hp wasused. The mixing and agglomeration speed of the impeller were set to1500 rpm. This rotation speed allowed the slurry to remain fluidized atall conditions of the experiments. The agglomeration experiments wereconducted at room temperature (22° C.).

The agglomerated solids produced in these experiments were treated in aSoxhlet extractor combined with Dean-Stark azeotropic distillation, todetermine the material contents of the agglomerated slurry. Toluene wasused as the extraction solvent. The oil sand solids were dried overnightin an oven (100° C.) and then weighed to determine the solids content ofthe agglomerated slurry. The water content was determined by measuringthe volume of the collected water within the side arm of the Dean-Starkapparatus. The bitumen content of the agglomerated slurry was determinedby evaporating the toluene and residual cyclohexane from an aliquot ofthe hydrocarbon extract from the Soxhlet extractor.

The initial liquid drainage rate was calculated by measuring the timeneeded to drain 50 mL of bitumen extract above the bed of agglomeratedsolids.

Experiment 1 Agglomeration by Adding all the Bridging Liquid at OneStage

350 g of oil sands and 235.07 g of extraction liquor were placed intothe Parr reactor vessel. The solids and solvent were mixed at 1500 rpmfor 5 minutes to homogenize the mixture and to extract the bitumen thatwas in the oil sands. After 5 minutes of mixing, 16.8 g of water wasquickly poured into the vessel through a sample port. The mixture wasthen mixed at 1500 rpm for an additional 2 minutes to agglomerate thesolids.

After the agglomeration process, the impeller was turned off and theagglomerates were allowed to settle for over 1 minute. The supernatant(bitumen extract) was poured into a separate container and the wetsolids were transferred to a Buchner funnel. The solids rested on afilter paper with a nominal pore size of 170 μm. The filter's effectivearea was approximately 8 cm². The solids bed height was 10.8 cm. Aportion of the collected supernatant was poured on top of the solidsuntil a liquid height of 1.9 cm formed above the solids surface. A lightvacuum was then applied to the Buchner funnel and the initial drainagerate of the liquid was recorded. The initial drainage rate for solidsagglomerated by adding all the bridging liquid at one stage to thesolids slurry was 0.35 mL/(cm² sec).

The remaining supernatant was poured onto the solid bed and allowed tofilter through. 211 mL of pure cyclohexane was then filtered through thesolid bed in order to wash the agglomerates. The solid bed was thenallowed to drain of liquid under a light vacuum for about 30 seconds.The bitumen content of the washed solids was then measured to determinethe bitumen recovery of the solvent extraction process. The bitumenrecovery from this solvent extraction with solids agglomeration processwas 87%.

Experiment 2 Agglomeration by Adding all the Bridging Liquid at OneStage

The same conditions as Experiment 1 was repeated with the agglomerationtime extended to 15 minutes instead of 2 minutes. The initial drainagerate for solids agglomerated by adding all the bridging liquid at onestage and extending the agglomeration time increased to 1.6 mL/(cm²sec). However, the bitumen recovery for this extraction process droppedto 83.8%.

Experiment 3 Agglomeration by Using Staged Addition of Bridging Liquidto Solids Slurry

350 g of oil sands and 235.07 g of extraction liquor were placed intothe Parr reactor vessel. The solids and solvent were mixed at 1500 rpmfor 5 minutes to fully homogenize the mixture and to fully extract thebitumen that was in the oil sands. After 5 minute of mixing, 5.6 g ofwater was poured into the vessel through a sample port and the mixturewas mixed for 30 seconds. Subsequently, 5.6 g of water was poured intothe vessel and the mixture was mixed for an additional 30 seconds.Lastly, 5.6 g of water was poured into the vessel and the mixture wasmixed for 1 minutes. All mixing was done at room temperature.

After the agglomeration process the impeller was turned off and theagglomerates were allowed to settle for over 1 minute. The supernatant(bitumen extract) was poured into a separate container and the wetsolids were transferred to a Buchner funnel. The solids rested on afilter paper with a nominal pore size of 170 μm. The filter's effectivearea was approximately 8 cm². The solids bed height was 10.8 cm. Aportion of the collected supernatant was poured on top of the solidsuntil a liquid height of 1.9 cm formed above the solids surface. A lightvacuum was then applied to the Buchner funnel and the initial drainagerate of the liquid was recorded. The initial drainage rate for solidsagglomerated by adding bridging liquid in three separate stages to thesolids slurry was 1.04 mL/(cm² sec).

The remaining supernatant was poured onto the solid bed and allowed tofilter though. 211 mL of pure cyclohexane was then filtered through thesolid bed in order to wash the agglomerates. The solid bed was thenallowed to drain of liquid under a light vacuum for about 30 seconds.The bitumen content of the washed solids was then measured to determinethe bitumen recovery of the solvent extraction process. The bitumenrecovery from this solvent extraction with solids agglomeration processwas 86.3%.

The drainage rate of the agglomerates formed by using staged addition ofthe bridging liquid was approximately 3 times greater than that ofagglomerates formed when all the bridging liquid is added in one stage(compare Experiment 3 to Experiment 1). The drainage rate of the singlestage agglomeration process can be increased by extending theagglomeration time (see Experiment 2) in order to form largeragglomerates. However, the larger agglomerates results in a reduction inthe bitumen recovery. In contrast, the staged addition of bridgingliquid resulted in an increase in drainage rate without a significantreduction in bitumen recovery. Visual inspection of Experiment 3agglomerates did not reveal significantly larger agglomerates comparedto the agglomerates of Experiment 1. This suggests that the fasterdrainage rate of the agglomerates formed by staged addition of bridgingliquid is due to more uniform agglomerates rather than largeragglomerates.

1. A method of processing a bituminous feed, the method comprising: a)contacting the bituminous feed with an extraction liquor to form aslurry, wherein the extraction liquor comprises a solvent; b) adding abridging liquid to the slurry in at least two stages and agitatingsolids within the slurry to form an agglomerated slurry comprisingagglomerates and a low solids bitumen extract; said bridging liquidbeing added to the slurry in regions having higher shear rates than amedian shear rate within the slurry; and c) separating the agglomeratesfrom the low solids bitumen extract.
 2. The method of claim 1, whereinthe regions having higher shear rates than a median shear rate withinthe slurry are regions adjacent propellers used to agitate the slurry.3. The method of claim 2, wherein the propellers comprise ports foradding the bridging liquid to the slurry.
 4. The method of claim 1,wherein the bridging liquid is one of (i) added in at least two stagesin a single agglomerator, (ii) added continuously or intermittently inone or more agglomerators, (iii) added in at least two agglomerators,and (iv) added in at least three stages. 5.-6. (canceled)
 7. The methodof claim 1, wherein step b) comprises: i) adding a first portion of thebridging liquid to the slurry; ii) agitating solids within the slurry toform agglomerates; iii) removing agglomerates from the slurry to form asolids-reduced slurry; iv) adding a second portion of the bridgingliquid to the solids-reduced slurry; and v) agitating solids within thesolids-reduced slurry to form agglomerates.
 8. The method of claim 7,one of (1) wherein steps i) to v) are performed at least twice, (2)wherein the first portion of the bridging liquid is added to a firstagglomerator, the second portion of the bridging liquid is added to asecond agglomerator, and agglomerates are removed to form thesolids-reduced slurry using a solid-liquid separator and (3) furthercomprising comminuting removed agglomerates of step iii), wherein one of(i) the comminuting is effected in an attrition scrubber and (ii) thecomminuting is effected in a mill. 9.-12. (canceled)
 13. The method ofclaim 1, wherein bridging liquid added during a first stage has one of(i) a salinity that is at least 10% higher or lower than a salinity of abridging liquid added during a second, subsequent stage and (ii) asuspended solids content that is at least 10% higher or lower than asuspended solids content of a bridging liquid added during a second,subsequent stage. 14.-15. (canceled)
 16. The method of claim 1, furthercomprising recovering the solvent from the low solids bitumen extract toform a bitumen product.
 17. The method of claim 16, further comprisingwashing the agglomerates of step c) with one of (i) the solventrecovered from the low solids bitumen extract and (ii) a solvent, whichsolvent is the same as or different from the solvent of step a), toextract additional bitumen and to form washed agglomerates. 18.(canceled)
 19. The method of claim 17, further comprising recoveringsolvent from one of (i) the agglomerates, which have been separated fromthe low solids bitumen extract and ii the washed agglomerates. 20.(canceled)
 21. The method of claim 1, wherein the extraction liquorcomprises the solvent of step a) and bitumen in an amount of 10 to 50 wt%.
 22. The method of claim 1, further comprising, prior to step a),contacting the bituminous feed with additional extraction liquor tobegin extraction.
 23. The method of claim 1, wherein the bridging liquidis one of water and an aqueous solution.
 24. (canceled)
 25. The methodof claim 1, wherein at least 80 wt. % of the agglomerates of step c) arebetween 0.1 and 1 mm.
 26. The method of claim 1, wherein theagglomerated slurry has a solids content of 20 to 70 wt %.
 27. Themethod of claim 1, wherein the solvent comprises at least one of (i) anorganic solvent or a mixture of organic solvents and (ii) a paraffinicsolvent, a cyclic aliphatic hydrocarbon, or a mixture thereof. 28.(canceled)
 29. The method of claim 27, wherein the paraffinic solventcomprises an alkane, a natural gas condensate, a distillate from afractionation unit, or a combination thereof containing more than 40%small chain paraffins of 5 to 10 carbon atoms.
 30. The method of claim27, wherein the alkane comprises one of (i) normal alkane, an isoalkane,or a combination thereof and (ii) heptane, iso-heptane, hexane,iso-hexane, pentane, iso-pentane, or a combination thereof. 31.(canceled)
 32. The method of claim 27, wherein the cyclic aliphatichydrocarbon comprises a cycloalkane of 4 to 9 carbon atoms, and whereinthe cycloalkane comprises cyclohexane, cyclopentane, or a mixturethereof.
 33. (canceled)
 34. The method of claim 1, wherein the solventcomprises at least 50 wt. % cyclohexane.
 35. The method of claim 1,wherein one of the extraction liquor comprises residual solids and thebridging liquid comprises solid fines, and wherein bridging liquid has asolids content of less than 40 wt % solid fines. 36.-37. (canceled) 38.The method of claim 1, wherein a ratio of the solvent to bitumen in theagglomerated slurry is less than 2:1.
 39. The method of claim 1, whereinstep b) comprises agitating by mixing, shaking, or rolling. 40.(canceled)
 41. The method of claim 1, wherein a ratio of bridging liquidplus connate water from the bituminous feed to solids within theagglomerated slurry is in the range of 0.02 to 0.25.
 42. (canceled)